green energy physics unit 5. classification renewable/ non conventional non renewable/ conventional

Green energy Physics Unit 5

Classification Renewable/ non conventional Non renewable/ conventional

How much solar energy? The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable.

Direct Conversion into Electricity Photovoltaic cells are capable of directly converting sunlight into electricity. A simple wafer of silicon with wires attached to the layers. Current is produced based on types of silicon (n- and p-types) used for the layers. Each cell=0.5 volts. Battery needed as storage No moving parts do no wear out, but because they are exposed to the weather, their lifespan is about 20 years.

PH 0101 Unit-5 Lecture-25 A proper metal contacts are made on the n-type and p-type side of the semiconductor for electrical connection Working: When a solar panel exposed to sunlight, the light energies are absorbed by a semiconduction materials. Due to this absorded enrgy, the electrons are libereted and produce the external DC current. The DC current is converted into 240-volt AC current using an inverter for different applications.

PH 0101 Unit-5 Lecture-26 Mechanism: First, the sunlight is absorbed by a solar cell in a solar panel. The absorbed light causes electrons in the material to increase in energy. At the same time making them free to move around in the material. However, the electrons remain at this higher energy for only a short time before returning to their original lower energy position. Therefore, to collect the carriers before they lose the energy gained from the light, a PN junction is typically used.

PH 0101 Unit-5 Lecture-27 A PN junction consists of two different regions of a semiconductor material (usually silicon), with one side called the p type region and the other the n-type region. During the incident of light energy, in p-type material, electrons can gain energy and move into the n-type region. Then they can no longer go back to their original low energy position and remain at a higher energy. The process of moving a light- generated carrier from p- type region to n-type region is called collection. These collections of carriers (electrons) can be either extracted from the device to give a current, or it can remain in the device and gives rise to a voltage.

PH 0101 Unit-5 Lecture-28 The electrons that leave the solar cell as current give up their energy to whatever is connected to the solar cell, and then re-enter the solar cell. Once back in the solar cell, the process begins again:

PH 0101 Unit-5 Lecture-29 The mechanism of electricity production- Different stages Conduction band High density Valence band Low density E The above diagram shows the formation of p-n junction in a solar cell. The valence band is a low-density band and conduction band is high- density band.

PH 0101 Unit-5 Lecture-210 Stage-1 Therefore, the hole (vacancy position left by the electron in the valence band) is generates. Hence, there is a formation of electron- hole pair on the sides of p-n junction. When light falls on the semiconductor surface, the electron from valence band promoted to conduction band. Conduction band High density Valence bandLow density E

PH 0101 Unit-5 Lecture-211 Stage-2 In the stage 2, the electron and holes are diffuse across the p-n junction and there is a formation of electron-hole pair. Conduction band High density Valence bandLow density E junction

PH 0101 Unit-5 Lecture-212 Stage-3 In the stage 3, As electron continuous to diffuse, the negative charge build on emitter side and positive charge build on the base side. Conduction band High density Valence bandLow density E junction

PH 0101 Unit-5 Lecture-213 Stage-4 When the PN junction is connected with external circuit, the current flows. Conduction band High density Valence bandLow density E junction Power

PH 0101 Unit-5 Lecture-214 A solar panel (or) Solar array Single solar cell The single solar cell constitute the n-type layer sandwiched with p-type layer. The most commonly known solar cell is configured as a large-area p-n junction made from silicon wafer. A single cell can produce only very tiny amounts of electricity It can be used only to light up a small light bulb or power a calculator. Single photovoltaic cells are used in many small electronic appliances such as watches and calculators

PH 0101 Unit-5 Lecture-215 N-type P-type Single Solar cell

PH 0101 Unit-5 Lecture-216 Solar panel (or) solar array (or) Solar module The solar panel (or) solar array is the interconnection of number of solar module to get efficient power. A solar module consists of number of interconnected solar cells. These interconnected cells embedded between two glass plate to protect from the bad whether. Since absorption area of module is high, more energy can be produced.

PH 0101 Unit-5 Lecture-217

PH 0101 Unit-5 Lecture-218 Based on the types of crystal used, soar cells can be classified as, 1.Monocrystalline silicon cells 2.Polycrystalline silicon cells 3.Amorphous silicon cells 1.The Monocrystalline silicon cell is produced from pure silicon (single crystal). Since the Monocrystalline silicon is pure and defect free, the efficiency of cell will be higher. 2.In polycrystalline solar cell, liquid silicon is used as raw material and polycrystalline silicon was obtained followed by solidification process. The materials contain various crystalline sizes. Hence, the efficiency of this type of cell is less than Monocrystalline cell. Types of Solar cell

PH 0101 Unit-5 Lecture-219 3. Amorphous silicon was obtained by depositing silicon film on the substrate like glass plate. The layer thickness amounts to less than 1m the thickness of a human hair for comparison is 50-100 m. The efficiency of amorphous cells is much lower than that of the other two cell types. As a result, they are used mainly in low power equipment, such as watches and pocket calculators, or as facade elements.

PH 0101 Unit-5 Lecture-220 Comparison of Types of solar cell MaterialEfficiency (%) Monocrystalline silicon14-17 Polycrystalline silicon13-15 Amorphous silicon5-7

PH 0101 Unit-5 Lecture-221 Advantage, disadvantage and application of Solar cell Advantage 1.It is clean and non-polluting 2.It is a renewable energy 3.Solar cells do not produce noise and they are totally silent. 4.They require very little maintenance 5.They are long lasting sources of energy which can be used almost anywhere 6.They have long life time 7.There are no fuel costs or fuel supply problems

PH 0101 Unit-5 Lecture-222 Disadvantage 1.Solar power cant be obtained in night time 2.Solar cells (or) solar panels are very expensive 3.Energy has not be stored in batteries 4.Air pollution and whether can affect the production of electricity 5.They need large are of land to produce more efficient power supply

WIND POWER What is it? How does it work? Efficiency

WIND POWER - What is it? All renewable energy (except tidal and geothermal power), ultimately comes from the sun The earth receives 2 x 10 17 watts of power (per hour) from the sun About 2 percent of this energy is converted to wind energy Differential heating of the earths surface and atmosphere induces vertical and horizontal air currents that are affected by the earths rotation and contours of the land WIND. ~ e.g.: Land Sea Breeze Cycle

Wind is slowed by the surface roughness and obstacles. A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. The kinetic energy of a moving body is proportional to its weight. In other words, the "heavier" the air, the more energy is received by the turbine.

KidWind Project | www.kidwind.org

LARGE TURBINES: Able to deliver electricity at lower cost than smaller turbines, because foundation costs, planning costs, etc. are independent of size. Well-suited for offshore wind plants. In areas where it is difficult to find sites, one large turbine on a tall tower uses the wind extremely efficiently.

SMALL TURBINES: Local electrical grids may not be able to handle the large electrical output from a large turbine, so smaller turbines may be more suitable. High costs for foundations for large turbines may not be economical in some areas. Landscape considerations

Wind Turbines: Number of Blades Most common design is the three-bladed turbine. The most important reason is the stability of the turbine. A rotor with an odd number of rotor blades (and at least three blades) can be considered to be similar to a disc when calculating the dynamic properties of the machine. A rotor with an even number of blades will give stability problems for a machine with a stiff structure.

Wind power generators convert wind energy (mechanical energy) to electrical energy. The generator is attached at one end to the wind turbine, which provides the mechanical energy. At the other end, the generator is connected to the electrical grid. The generator needs to have a cooling system to make sure there is no overheating.

*No other factor is more important to the amount of power available in the wind than the speed of the wind The power in wind is proportional to the cubic wind speed ( v^3 ). 20% increase in wind speed means 73% more power Doubling wind speed means 8 times more power WHY? ~ Kinetic energy of an air mass is proportional to v^2 ~ Amount of air mass moving past a given point is proportional to wind velocity (v)

Calculation of Wind Power Power in the wind Effect of air density, Effect of swept area, A Effect of wind speed, V R Swept Area: A = R 2 Area of the circle swept by the rotor (m 2 ). Power in the Wind = AV 3

Environmental benefits No emissions No fuel needed Distributed power Remote locations

Limitations of Wind Power Power density is very low. Needs a very large number of wind mills to produce modest amounts of power. Cost. Environmental costs. material and maintenance costs. Noise, birds and appearance. Cannot meet large scale and transportation energy needs.

The Future of Wind Energy Future of wind energy can be bright if government policies subsidize and encourage its use. Technology improvements unlikely to have a major impact. Can become cost competitive for electricity generation if fossil energy costs skyrocket.

Ocean Energy Thermal energy-OTEC(Ocean Thermal Electric Conversion) Mechanical energy From tides From waves

Wave Facts: Waves are caused by a number of forces, i.e. wind, gravitational pull from the sun and moon, changes in atmospheric pressure, earthquakes etc. Waves created by wind are the most common waves. Unequal heating of the Earths surface generates wind, and wind blowing over water generates waves. Wave energy is an irregular and oscillating low-frequency energy source that must be converted to a 50-Hertz frequency before it can be added to the electric utility grid. Mechanical energy-From waves

Three Basic Kinds of Systems Offshore (so your dealing with swell energy not breaking waves) Near Shore (maximum wave amplitude) Embedded devices (built into shoreline to receive breaking wave but energy loss is occurring while the wave is breaking)

3 basic systems for ocean wave energy devices 1. Channel systems that funnel waves into reservoirs 2. Float systems that drive hydraulic pumps 3. Oscillating water column systems that use waves to compress air within a container mechanical power either directly activates a generator, or transfers to a working fluid, water or air, which then drives a turbine/generator

Wave Power Designs Wave Surge or Focusing Devices-Channel System These shoreline devices, also called "tapered channel" systems, rely on a shore-mounted structure to channel and concentrate the waves, driving them into an elevated reservoir. These focusing surge devices are sizable barriers that channel large waves to increase wave height for redirection into elevated reservoirs. Wave Surge or Focusing Devices

Floats or Pitching Devices Floats or Pitching Devices These devices generate electricity from the bobbing or pitching action of a floating object. The object can be mounted to a floating raft or to a device fixed on the ocean floor.

17-42 Oscillating Water Columns (OWC) Oscillating Water Columns (OWC) These devices generate electricity from the wave-driven rise and fall of water in a cylindrical shaft. The rising and falling water column drives air into and out of the top of the shaft, powering an air-driven turbine.

-Advantages and Disadvantages- Advantages The energy is free no fuel needed, no waste produced Not expensive to operate and maintain Can produce a great deal of energy Disadvantages Depends on the waves sometimes youll get loads of energy, sometimes almost nothing Needs a suitable site, where waves are consistently strong Some designs are noisy. But then again, so are waves, so any noise is unlikely to be a problem Must be able to withstand

Tidal Power Tidal power generators derive their energy from movement of the tides. Has potential for generation of very large amounts of electricity, or can be used in smaller scale.

Tides The interaction of the Moon and the Earth results in the oceans bulging out towards the Moon (Lunar Tide). The suns gravitational field pulls as well (Solar Tide) As the Sun and Moon are not in fixed positions in the celestial sphere, but change position with respect to each other, their influence on the tidal range (difference between low and high tide) is also effected. If the Moon and the Sun are in the same plane as the Earth, the tidal range is the superposition of the range due to the lunar and solar tides. This results in the maximum tidal range (spring tides). If they are at right angles to each other, lower tidal differences are experienced resulting in neap tides.

How do tides changing = Electricity? As usual, the electricity is provided by spinning turbines. Two types of tidal energy can be extracted: kinetic energy of currents between ebbing (tide going out) and surging tides(tide coming in) and potential energy from the difference in height (or head) between high and low tides. The potential energy contained in a volume of water is E = xMg where x is the height of the tide, M is the mass of water and g is the acceleration due to gravity.

1.) Tidal Barrage Two types: Single basin system Double-basin system Utilize potential energy Tidal barrages are typically dams built across an estuary or bay. consist of turbines, sluice gates, embankments, and ship locks. Basin

Single basin system- Ebb generation: During flood tide basin is filled and sluice gates are closed, trapping water. Gates are kept closed until the tide has ebbed sufficiently and thus turbines start spinning and generating electricity. Flood generation: The basin is filled through the turbine which generate at flood tide. Two way generation: Sluice gates and turbines are closed until near the end of the flood tide when water is allowed to flow through the turbines into the basin creating electricity. At the point where the hydrostatic head is insufficient for power generation the sluice gates are opened and kept open until high tide when they are closed. When the tide outside the barrage has dropped sufficiently water is allowed to flow out of the basin through the turbines again creating electricity.

Double-basin system There are two basins, but it operates similar to en ebb generation, single-basin system. The only difference is a proportion of the electricity is used to pump water into the second basin allowing storage.

Ocean Thermal Energy Conversion Ocean thermal energy conversion (OTEC) is a method for generating electricity which uses the temperature difference that exists between deep and shallow waters

The ocean stores thermal energy Each day, the tropical oceans absorb an amount of solar radiation equal to the heat content of 250 billion barrels of oil The oceans surface is warmer than deep water -Ocean thermal energy conversion (OTEC) is based on this gradient in temperature -Closed cycle approach = warm surface water evaporates chemicals, which spin turbines -Open cycle approach = warm surface water is evaporated in a vacuum and its steam turns turbines -Costs remain high and no facility is commercially operational 17-52

OTEC: What is it? Thermal energy- form of energy that manifests itself as an increase of temp. Thermal energy- form of energy that manifests itself as an increase of temp. Method for generating electricity. Method for generating electricity. Runs a heat engine- a physical device that converts thermal energy to mechanical output Runs a heat engine- a physical device that converts thermal energy to mechanical output Uses temp. difference that exists b/w deep & shallow waters. Uses temp. difference that exists b/w deep & shallow waters. Temperature difference between warm surface water and cold deep water must be >20C (36F) for OTEC system to produce significant power. Temperature difference between warm surface water and cold deep water must be >20C (36F) for OTEC system to produce significant power.

Ocean Thermal Energy Conversion (OTEC) Ocean Thermal Energy Conversion produces electricity from the natural thermal gradient of the ocean, using the heat stored in warm surface water to create steam to drive a turbine, while pumping cold, deep water to the surface to re- condense the steam. Ocean Thermal Energy Conversion produces electricity from the natural thermal gradient of the ocean, using the heat stored in warm surface water to create steam to drive a turbine, while pumping cold, deep water to the surface to re- condense the steam.

Closed Cycle OTEC In closed-cycle OTEC, warm seawater heats a working fluid, such as ammonia, with a low boiling point, such as ammonia, which flows through a heat exchanger (evaporator). The ammonia vapor expands at moderate pressures turning a turbine, which drives a generator which produces energy.

OTEC: Closed Cycle The vapor is then condensed in another heat exchanger (condenser) by the cold, deep-ocean water running through a cold water pipe. The working fluid (ammonia) is then cycled back through the system, being continuously recycled.

Ocean Thermal Energy Conversion (OTEC)

Open Cycle OTEC In an open-cycle OTEC plant, warm seawater from the surface is the working fluid that is pumped into a vacuum chamber where it is flash- evaporated to produce steam at an absolute pressure of about 2.4 kilopascals (kPa). The resulting steam expands through a low-pressure turbine that is hooked up to a generator to produce electricity. The steam that exits the turbine is condensed by cold, deep-ocean water, which is returned to the environment. If a surface condenser is used, the condensed steam remains separated from the cold ocean water and can be collected as a ready source of desalinated water for commercial, domestic or agricultural use.

OTEC Open Cycle System In an open-cycle plant, the warm water, after being vaporized, can be re-condensed and separated from the cold seawater, leaving behind the salt and providing a source of desalinated water fresh enough for municipal or agricultural use. In an open-cycle plant, the warm water, after being vaporized, can be re-condensed and separated from the cold seawater, leaving behind the salt and providing a source of desalinated water fresh enough for municipal or agricultural use.

OTEC Hybrid Cycle System Hybrid plants, combining benefits of the two systems, would use closed-cycle generation combined with a second-stage flash evaporator to desalinate water.

OTEC limited applications Very costly Limited suitable sites cant justify for electricity must also desalinize, sustain aquaculture, etc

Geothermal Energy

Sources of Earths Internal Energy 70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth Some energy is from residual heat left over from Earths formation. The rest of the energy comes from meteorite impacts. Geothermal energy Renewable energy is generated from deep within the Earth Radioactive decay of elements under extremely high pressures deep inside the planet generates heat -This heat rises through magma, fissures, and cracks Geothermal power plants use heated water and steam for direct heating and generating electricity

Different Geothermal Energy Sources 1.Hydrothermal resources: a)Hot Water Reservoirs: As the name implies these are reservoirs of hot underground water. There is a large amount of them in the US, but they are more suited for space heating than for electricity production. b)Natural Stem Reservoirs: In this case a hole dug into the ground can cause steam to come to the surface. This type of resource is rare in the US.

2.Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock. This type of resource can be used for both heat and for natural gas. Normal Geothermal Gradient: At any place on the planet, there is a normal temperature gradient of +30 0 C per km dug into the earth. Therefore, if one digs 20,000 feet the temperature will be about 190 0 C above the surface temperature. This difference will be enough to produce electricity. However, no useful and economical technology has been developed to extracted this large source of energy. 3.Molten Magma: No technology exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii.

4.Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to Normal Geothermal Gradient, but the gradient is 40 0 C/km dug underground. The simplest models have one injection well and two production wells. Pressurized cold water is sent down the injection well where the hot rocks heat the water up. Then pressurized water of temperatures greater than 200 0 F is brought to the surface and passed near a liquid with a lower boiling temperature, such as an organic liquid like butane. The ensuing steam turns the turbines. Then, the cool water is again injected to be heated. This system does not produce any emissions. US geothermal industries are making plans to commercialize this new technology.

Geothermal energy is renewable in principle But if a geothermal plant uses heated water faster than groundwater is recharged, the plant will run out of water -Operators have begun injecting municipal wastewater into the ground to replenish the supply 17-67

We can harness geothermal energy for heating and electricity Geothermal ground source heat pumps (GSHPs) use thermal energy from near-surface sources of earth and water -The pumps heat buildings in the winter by transferring heat from the ground into buildings -In the summer, heat is transferred through underground pipes from the building into the ground -Highly efficient, because heat is simply moved 17-68

Use of geothermal power is growing Currently, geothermal energy provides less than 0.5% of the total energy used worldwide -It provides more power than solar and wind combined -But much less than hydropower and biomass Commercially viable only in British Columbia In the right setting, geothermal power can be among the cheapest electricity to generate 17-69

Geothermal power has benefits and limitations Benefits: -Reduces emissions -It does emit very small amounts of gases Limitations: -May not be sustainable, as CO 2 can be released -Water is laced with salts and minerals that corrode equipment and pollute the air -Limited to areas where the energy can be trapped 17-70

Biomass Biomass is a renewable energy source that is derived from living or recently living organisms. Biomass includes biological material, not organic material like coal. Energy derived from biomass is mostly used to generate electricity or to produce heat. Thermal energy is extracted by means of combustion, torrefaction, pyrolysis, and gasification. Biomass can be chemically and biochemically treated to convert it to a energy-rich fuel.

72 Biomass Resources Energy Crops Woody crops Agricultural crops Waste Products Wood residues Temperate crop wastes Tropical crop wastes Animal wastes Municipal Solid Waste (MSW) Commercial and industrial wastes http://www.eere.energy.gov/RE/bio_resources.html

Conversion Technologies A wide variety of technologies is deployed for energy production from biomass Production of heat, electricity and transport fuels is possible through a portfolio of technologies

Conversion technologies: power and heat Digestion : Biogas is released with the digestion of organic material Combustion: Because heat releases with the combustion of biomass, electricity can be aroused using a steam turbine Gasification: high heating of organic material, releases biogas Production of bio-oils

Conversion technologies: biofuels for the transport Sector Extraction and production of esters from oilseeds Fermentation: production of ethanol Methanol, hydrogen and hydrocarbons via Gasification

ENVIRONMENTAL ADVANTAGES Renewable resource Reduces landfills Protects clean water supplies Reduces acid rain and smog Reduces greenhouse gases Carbon dioxide Methane

BIOMASS AND CARBON EMMISIONS Biomass emits carbon dioxide when it naturally decays and when it is used as an energy source Living biomass in plants and trees absorbs carbon dioxide from the atmosphere through photosynthesis Biomass causes a closed cycle with no net emissions of greenhouse gases

GEOGRAPHIC AREAS Comes from the forest Can also come from plant and animal waste Wood and waste can be found virtually anywhere Transportation costs

Introduction: What is Biodiesel? A diesel fuel replacement produced from vegetable oils or animal fats through the chemical process of transesterification Mono-alkyl esters Biodiesel can be used in any diesel motor in any percent from 0-100% with little or no modifications to the engine

Why make biodiesel? Diesel fuel injectors are not designed for viscous fuels like vegetable oil Glycerin (thick) Biodiesel

The Chemistry of Biodiesel All fats and oils consist of triglycerides Glycerol/glycerine = alcohol 3 fatty acid chains (FA) Transesterification describes the reaction where glycerol is replaced with a lighter and less viscous alcohol e.g. Methanol or ethanol A catalyst (KOH or NaOH) is needed to break the glycerol-FA bonds

Transesterification (the biodiesel reaction) Fatty Acid Chain Glycerol Methanol (or Ethanol) One triglyceride molecule is converted into three mono alkyl ester (biodiesel) molecules Biodiesel Triglyceride

Vegetable Oil as Feedstocks Oil-seed crops are the focus for biodiesel production expansion Currently higher market values for competing uses constrain utilization of crops for biodiesel production Most oil-seed crops produce both a marketable oil and meal Seeds must be crushed to extract oil The meal often has higher market value than the oil

Soybeans Primary source for biodiesel production in U.S. Approximately 2 billion gallons of oil produced annually Canola/Rapeseed Rapeseed is a member of the mustard family Canola is a variety of rapeseed bred to have low levels of erucic acid and glucosinolates (both of which are undesireable for human consumption) Good oil yield

Sunflowers Wide geographical range for production Market value is high for edible oil and seeds, birdseeds Second largest biodiesel feedstock in the EU Camelina Camelina sativa is a member of mustard family Summer annual crop suited to grow in semi-arid climates and northern U.S.

Advantages of Biodiesel Biodegradable Non-toxic Favorable Emissions Profile Renewable Carbon Neutrality Requires no engine modifications (except replacing some fuel lines on older engines). Can be blended in any proportion with petroleum diesel fuel. Can be made from waste restaurant oils and animal fats

Disadvantages of biodiesel Lower Energy Content 8% fewer BTUs per gallon, but also higher cetane #, lubricity, etc. Poor cold weather performance This can be mitigated by blending with diesel fuel or with additives, or using low gel point feedstocks such as rapeseed/canola. Stability Concerns Biodiesel is less oxidatively stable than petroleum diesel fuel. Old fuel can become acidic and form sediments and varnish. Additives can prevent this. Scalability Current feedstock technology limits large scalability

Fuel Cells

PEM Fuel Cell

Parts of a Fuel Cell Anode Negative post of the fuel cell. Conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. Etched channels disperse hydrogen gas over the surface of catalyst. Cathode Positive post of the fuel cell Etched channels distribute oxygen to the surface of the catalyst. Conducts electrons back from the external circuit to the catalyst Recombine with the hydrogen ions and oxygen to form water. Electrolyte Proton exchange membrane. Specially treated material, only conducts positively charged ions. Membrane blocks electrons. Catalyst Special material that facilitates reaction of oxygen and hydrogen Usually platinum powder very thinly coated onto carbon paper or cloth. Rough & porous maximizes surface area exposed to hydrogen or oxygen The platinum-coated side of the catalyst faces the PEM.

Fuel Cell Operation Pressurized hydrogen gas (H 2 ) enters cell on anode side. Gas is forced through catalyst by pressure. When H 2 molecule comes contacts platinum catalyst, it splits into two H+ ions and two electrons (e-). Electrons are conducted through the anode Make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell. On the cathode side, oxygen gas (O 2 ) is forced through the catalyst Forms two oxygen atoms, each with a strong negative charge. Negative charge attracts the two H+ ions through the membrane, Combine with an oxygen atom and two electrons from the external circuit to form a water molecule (H 2 O).

Proton-Exchange Membrane Cell http://www.news.cornell.edu/releases/Nov03/Fuelcell.institute.deb.html

Fuel Cell Energy Exchange http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/electrol.html

PEM Fuel Cell Schematic

Hydrogen Fuel Cell Efficiency 40% efficiency converting methanol to hydrogen in reformer 80% of hydrogen energy content converted to electrical energy 80% efficiency for inverter/motor Converts electrical to mechanical energy Overall efficiency of 24-32%

Auto Power Efficiency Comparison Technology System Efficiency Fuel Cell24-32% Electric Battery26% Gasoline Engine20% http://www.howstuffworks.com/fuel-cell.htm/printable

Other Types of Fuel Cells Alkaline fuel cell (AFC) This is one of the oldest designs. It has been used in the U.S. space program since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized.space Phosphoric-acid fuel cell (PAFC) The phosphoric-acid fuel cell has potential for use in small stationary power- generation systems. It operates at a higher temperature than PEM fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars. Solid oxide fuel cell (SOFC) These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (around 1,832 F, 1,000 C). This high temperature makes reliability a problem, but it also has an advantage: The steam produced by the fuel cell can be channeled into turbines to generate more electricity. This improves the overall efficiency of the system. Molten carbonate fuel cell (MCFC) These fuel cells are also best suited for large stationary power generators. They operate at 1,112 F (600 C), so they also generate steam that can be used to generate more power. They have a lower operating temperature than the SOFC, which means they don't need such exotic materials. This makes the design a little less expensive. http://www.howstuffworks.com/fuel-cell.htm/printable

Advantages/Disadvantages of Fuel Cells Advantages Water is the only discharge (pure H 2 ) Disadvantages CO 2 discharged with methanol reform Little more efficient than alternatives Technology currently expensive Many design issues still in progress Hydrogen often created using dirty energy (e.g., coal) Pure hydrogen is difficult to handle Refilling stations, storage tanks,

What is a Gas Hydrate? A gas hydrate is a crystalline solid; its building blocks consist of a gas molecule surrounded by a cage of water molecules. It is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Suitable gases are: carbon dioxide, hydrogen sulfide, and several low-carbon-number hydrocarbons. Most gas hydrates, however are Methane Hydrates.

What are Methane Hydrates? Methane Hydrates are one example of clathrates Clathrates are compounds which consist of a cage structure, in which a gas molecule is trapped inside a cage of water molecules Methane (CH 4 ) is trapped in Water (H 2 O) forming an ICE

1 m 3 of hydrate -> ~170 m 3 methane gas (STP) Grey=carbon Green=hydrogen in CH 4 Red = oxygen White= hydrogen in H 2 O

Hydrate Samples Gas hydrates in sea-floor mounds Here methane gas is actively dissociating from a hydrate mound. Gas hydrate can occur as nodules, laminae, or veins within sediment.

Gas Hydrate on the Sea floor Beasties!

Origin of natural methane Bacterial degradation of organic matter in low-oxygen environments within sediments Thermal degradation of organic matter, dominantly in petroleum (e.g., Gulf of Mexico)

Where do clathrates occur? How much clathrate is there? Methane and water must be available (organic matter: produced by biota; in oceans: close to continents) Clathrate must be stable (ice): cold and/or high pressure High latitudes (permafrost) In medium deep sea sediments (300-2000 m)

How much hydrate is there? Estimates vary widely: globally 600,000 to 2,000,000 Tcf (trillion cubic feet) 1 Tcf ~ 1 quadrillion Btu (quad) World energy use (2000): about 375-400 Quad = 500 Tcf hydrate gas per year US gas hydrates: estimated at about 100,000 to 600,000 Tcf Gas hydrates abundant in oil-poor countries (Japan, India)

Why are CH 4 Hydrates a good energy resource The gas is held in a crystal structure, therefore gas molecules are more densely packed than in conventional or other unconventional gas traps. Hydrate forms as cement in the pore spaces of sediment and has the capacity to fill sediment pore space and reduce permeability. CH 4 - hydrate-cemented strata thereby act as seals for trapped free gas Production of gas from hydrate-sealed traps may be an easy way to extract hydrate gas because the reduction of pressure caused by production can initiate a breakdown of hydrates and a recharging of the trap with gas

A Proposed Method For the gas production from hydrates and the seabed stability after the production, we proposed a new concept. The figure illustrates the molecular mining method by means of CO2 injection in order to extract CH4 from gas hydrate reservoirs. The concept is composed of three steps as follows; 1) injection of hot sea water into the hydrate layer to dissociate the hydrates, 2) produce gas from the hydrate, 3) inject CO2 to form carbon dioxide hydrate with residual water to hold the sea bed stable

CH 4 Hydrates and Climate Change Methane is a very effective greenhouse gas. It is ten times more potent than carbon dioxide. There is increasing evidence that points to the periodic massive release of methane into the atmosphere over geological timescales. Are these enormous releases of methane a cause or an effect of global climate change?

Global warming may cause hydrate destabilization through a rise in ocean bottom water temperatures. The increased methane content in the atmosphere in turn would be expected to accelerate warming, causing further dissociation, potentially resulting in run away global warming. Sea level rise, however, during warm periods may act to stabilize hydrates by increasing hydrostatic pressure, thereby acting as a check on warming. Hydrate dissociation may act as a check on glaciations, whereby reduced sea levels may cause seafloor hydrate dissociation, releasing methane and warming the climate.

CH 4 Hydrates and the Atmosphere An important aspect of methane hydrates and their affect on climate change is their potential to enter the atmosphere Methane concentration in seawater is observed to decrease by 98% between a depth of 300m and the sea surface as a result of microbial oxidation. The flux of methane into the atmosphere is thus lowered 50-fold (Mienert et al., 1998) However during catastrophic events such as largescale sediment slumping much higher proportions of methane would be released.

The Future of Methane Hydrates Worldwide gas production in the next 30-50 years Areas with unique economic and/or political motivations could see substantial production within 5-10 years We need to better understand the mechanisms of hydrate disassociation and its role in global warming, either as an accelerator or and inhibitor

Carbon Dioxide Emission: 24 billion tons per year

CARBON CAPTURE AND STORAGE Carbon capture and storage is mostly used to describe methods for removing CO 2 emissions from large stationary sources, such as electricity generation and some industrial processes, and storing it away from the atmosphere.

Carbon Capture Technology Post- combustion capture React the flue gas with chemicals that absorb CO 2 and then heat the chemicals to release CO 2. NOTE: Flue gas : Mixture of nitrogen, water vapor and 15 % of Carbon dioxide.

Carbon Capture Technology Pre- combustion capture Remove carbon before combustion. By gasifying the coal through the reaction with more oxygen, it is possible to a mix of mostly CO 2 and hydrogen.

Carbon Capture Technology Oxy-fuel combustion Use pure oxygen to support the fossil fuel combustion. The flue gas is then mostly CO 2 and water making it to separate easily.

Transportation Many point sources of captured CO 2 would not be close to geological or oceanic storage facilities. In these cases, transportation would be required. The main form of transportation pipeline. Shipping

CO2 storage Various forms have been conceived for permanent storage of CO2. These forms include gaseous storage in various deep geological formations (including saline formations and exhausted gas fields), liquid storage in the ocean, and solid storage by reaction of CO2 with metal oxides to produce stable carbonatesoxidescarbonates

Carbon Storage technology Geological storage Oceanic storage

Geological storage

Oceanic Storage Two storage mechanism has been proposed Dissolving CO 2 at mid-depth. Injecting the CO 2 at depths in excess of 3 km, where it would form lakes of liquid CO 2. Bellow 3 km liquid CO 2 would be denser than sea water and would sink to the ocean floor.

Carbon Storage Concerns CCS technologies actually require a lot of energy to implement and run transporting captured CO 2 by truck or ship, require fuel. Creating a CCS-enabled power plant also requires a lot of money. What happens if the carbon dioxide leaks out underground? We can't really answer this question. Because the process is so new, we don't know its long-term effects. Slow leakage would lead to climate changing. Sudden catastrophic leakage is dangerous, and causes asphyxiation. The more CO 2 an ocean surface absorbs, the more acidic it becomes, higher water acidity adversely affects marine life.

What might Carbon Capture and Storage look like? The diagram is from a BP news release from the abandoned Miller project, UK North Sea, which is no longer available online.

FutureGen FutureGen is a public-private partnership to build a first-of-its-kind coal- fueled, near-zero emissions power plant. It will use cutting-edge technologies to generate electricity while capturing and permanently storing carbon dioxide deep beneath the earth. The plant will also produce hydrogen and byproducts for possible use by other

132 the "forever fuel" that we can never run out of HYDROGEN Water + energy hydrogen + oxygen Hydrogen + oxygen water + energy

133 Hydrogen is ~75% of the known universe Hydrogen is ~75% of the known universe On earth, its not an energy source like oil or coal Only an energy carrier like electricity or gasoline Only an energy carrier like electricity or gasoline a form of energy, derived from a source, that can be a form of energy, derived from a source, that can be moved around moved around The most versatile energy carrier - Can be made from any source and used for any - Can be made from any source and used for any service service - Readily stored in large amounts - Readily stored in large amounts Why is hydrogen so important?

Sources of Hydrogen Sources that Hydrogen can be extracted from: Natural Gas, Water, Coal, Gasoline, Methanol, Biomass Other sources being researched include the uses of solar energy, photosynthesis, decomposition, and fuel cells themselves can tri-generate electricity, heat, and hydrogen.

135 Is it safe?: A primer on Hydrogen safety All fuels are hazardous, but All fuels are hazardous, but Hydrogen is comparably or less so, but Hydrogen is comparably or less so, but different: different: Clear flame cant sear you at a distance; no smoke smoke Hard to make explode; cant explode in free air; burns first air; burns first 22 less explosive power Rises, doesnt puddle Hindenburg myth (1937) nobody was killed Hindenburg myth (1937) nobody was killed by hydrogen fire by hydrogen fire Completely unrelated to hydrogen bombs

136 Where Does Hydrogen Come From? 95% of hydrogen is currently produced by steam reforming Partial Oxidation Steam Reforming Electrolysis Thermochemical Fossil Fuels Water Biomass currently most energy efficient requires improvements not cost effective requires high temperatures Gasification Microbial requiresimprovements slowkinetics

Hydrogen carries energy Most of the energy we use today94% comes from fossil fuels Fossil fuels are oil, coal, and natural gas and have developed over thousands of years from decomposing prehistoric plants and animalssince these plants and animals no longer exist, making new fossil fuels cannot happen. Only 6% of the energy we use comes from renewable energy sources But people want to use more renewable energy. It is usually cleaner and can be replenished in a short period of time compared to fossil fuels. The problem is that renewable energy sourceslike solar and windcant produce energy all the time The sun doesnt always shine. The wind doesnt always blow. Sometimes the sun and wind provide more energy than we need at that moment. Hydrogen can store and carry the energy until its needed and can be moved to where its needed.

Why are Energy Carriers good? Every day, we use more energy, mostly coal, to make electricity. Electricity is an energy carrier. Energy carriers can store, move, and deliver energy to consumers. We convert energy source like coal and natural gas to electricity because it is easier for us to move and use. Electricity gives us light, heat, hot water, cold food, TVs, and computers. Life would be really hard if we had to burn the coal, split the atoms, or build our own dams. Energy carriers make life easier. Hydrogen is an energy carrier like electricity. It can be used in places where its hard to use electricity. Electricity requires wires and poles, like you see along the highway and in your neighborhood, to be delivered to a home. Hydrogen can be shipped by a pipeline or produced at the home directly.

How does Hydrogen turn into useable Electricity? Hydrogen cannot directly make the lights turn on, the water run, or the heat work. It must be converted into electricity. This happens in a fuel cell. This is a real live fuel cell The only waste product is water

Uses for Hydrogen Energy NASA uses hydrogen as an energy carrier; it has used hydrogen for years in the space program. Hydrogen fuel lifts the space shuttle into orbit. Hydrogen fuel cells power the shuttles electrical systems. The only by-product is pure water, which the crew uses as drinking water. Hydrogen fuel cells are very efficient, but expensive to build. Small fuel cells can power electric cars. An engine that burns pure hydrogen produces almost no pollution. It will probably be many years, though, before you can walk into a car dealer and drive away in a hydrogen-powered car.

141 HYDROGEN IN TRANSPORTATION

Options for Storing Hydrogen Today

HYDROGEN STORAGE OPTIONS HYBRID TANKS LIQUID HYDROGEN COMPRESSED GAS PHYSICAL STORAGE Molecular H 2 REVERSIBLE

Compressed Storage Prototype vehicle tanks developed Efficient high-volume manufacturing processes needed Less expensive materials desired carbon fiber binder Evaluation of engineering factors related to safety required understanding of failure processes

Liquid Storage Prototype vehicle tanks developed Reduced mass and especially volume needed Reduced cost and development of high-volume production processes needed Extend dormancy (time to start of boil off loss) without increasing cost, mass, volume Improve energy efficiency of liquefaction

Hybrid Physical Storage Compressed H 2 @ cryogenic temperatures H 2 density increases at lower temperatures further density increase possible through use of adsorbents opportunity for new materials The best of both worlds, or the worst ?? Concepts under development

HYDROGEN STORAGE OPTIONS REVERSIBLE HYBRID TANKS LIQUID HYDROGEN COMPRESSED GAS PHYSICAL STORAGE Molecular H 2 REVERSIBLE CHEMICAL STORAGE Dissociative H 2 2 H COMPLEX METAL HYDRIDES CONVENTIONAL METAL HYDRIDES LIGHT ELEMENT SYSTEMS NON-REVERSIBLE REFORMED FUEL DECOMPOSED FUEL HYDROLYZED FUEL

Non-reversible On-board Storage On-board reforming of fuels has been rejected as a source of hydrogen because of packaging and cost energy station reforming to provide compressed hydrogen is still a viable option Hydrolysis hydrides suffer from high heat rejection on- board and large energy requirements for recycle On-board decomposition of specialty fuels is a real option need desirable recycle process engineering for minimum cost and ease of use

Reversible On-board Storage Reversible, solid state, on-board storage is the ultimate goal for automotive applications Accurate, fast computational techniques needed to scan new formulations and new classes of hydrides Thermodynamics of hydride systems can be tuned to improve system performance storage capacity temperature of hydrogen release kinetics/speed of hydrogen refueling Catalysts and additives may also improve storage characteristics

The Future of Hydrogen Before hydrogen becomes a significant fuel energy picture, many new systems must be built. We will need systems to make hydrogen, store it, and move it. We will need pipelines and economical fuel cells. And consumers will need the technology and the education to use it.

green energy physics unit 5. classification renewable/ non conventional non renewable/ conventional

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